Navigation Tab Text Colour

As seen in the above image, my navigation tabs aren't standing out from the background image. I would like to change the colour of the text on the non-selected tabs so that they stand out more and are more appealing. I tried going into Style Properties > Header & Navigation, and changing some of those options around, but the tab text didn't change colour. Could somebody assist me with this? I've never had to do this before. Thanks.